The present invention relates generally to providing a vertebral distractor for adjusting, particularly increasing, the distance between two vertebrae along the spinal axis when performing spinal procedures, particularly in the anterior cervical region, in conjunction with systems that use and generate images during medical and surgical procedures, which images assist in executing the procedures and indicate the relative position of various body parts and surgical instruments.
Vertebral distractors are known and are tools used during a spinal procedure, such as an anterior cervical procedure. Generally, the tool is used to increase the distance between two vertebral elements, such as vertebrae in a patient""s neck for the removal of damaged bone and/or the insertion of a bone graft into the damaged area. In particular, a vertebral distractor has two arms mounted in parallel on a shaft. The arms are movable in relation to each other.
To remove damaged bone and/or insert a bone graft, the arms of the vertebral distractor are engaged with or attached to different cervical vertebrae in the neck area. Certain vertebral distractors have arms with sharpened ends for gripping or otherwise engaging the vertebrae. The vertebrae are then pulled apart in a generally axial direction by manually increasing the distance between the arms of the distractor. While the vertebrae are distracted, the tension in the connecting soft tissues provides interbody rigidity. While the vertebrae remain distracted, surgical procedures can be performed, such as for example, damaged bone can be removed and new bone can be inserted.
During an anterior cervical spinal procedure, the vertebral distractor is positioned on either side of the throat area. In some cases, more than one vertebral distractor is used and is positioned such that there is a distractor on each side of the throat. This allows for more even distraction of the vertebrae. In positioning the vertebral distractor and engaging with or attaching it to the vertebrae of the patient, and, further, in completing the anterior cervical spinal surgery, the surgeon may have limited visual ability to determine the exact position of the vertebral distractor or the vertebrae with which the arms of the distractor are engaged.
Computer assisted image guided surgical navigation systems have been described that include indications of the relative positions of medical instruments and body parts used in medical or surgical procedures. For example, U.S. Pat. No. 5,383,454 to Bucholz; PCT Application No. PCT/US94/04530 (Publication No. WO 94/24933) to Bucholz; and PCT Application No. PCT/US95/12894 (Publication No. WO 96/11624) to Bucholz et al., the entire disclosures of which are incorporated herein by reference, disclose systems for use during a medical or surgical procedure using scans generated by a scanner prior to the procedure. Surgical navigation systems typically include tracking element such as for example an LED or reflector array on the body part and the medical instruments, a digitizer to track the positions of the body part and the instruments, and a display for the position of an instrument used in a medical procedure relative to a body part.
Accordingly, the present invention is directed to a vertebral distractor and a system for using a vertebral distractor in performing anterior surgery, particularly cervical spinal surgery. More specifically, an object of the present invention is directed to an apparatus for distraction or maintaining the relative position of at least two vertebrae in the cervical spinal area in conjunction with an image guided surgery system.
To achieve this object and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention includes a vertebral distractor for use in performing anterior cervical spinal surgery. The vertebral distractor is used in conjunction with a computer controlled surgical navigation system employing a position sensing unit to track positions of the vertebral distractor in three dimensional space relative to a known reference point. The vertebral distractor comprises a shaft having first and second arms attached to the shaft movable with respect to each other. The first and second arms are engageable with the vertebrae, such as by gripping or pinning. Moreover, the second arm is movable with relation to the first arm as the arms are engaged with the vertebrae for adjusting the distance between the vertebrae. At least one tracking array is attached to the shaft for tracking the location of the vertebral distractor as it is used to increase the distance between the vertebrae. One preferred tracking array includes tracking elements such as at least three LEDs.
Moreover, the preferred first and second arms each have extensions located at the distal end for engaging the vertebrae in the cervical spinal region. It is further preferred that the extensions be pins, although other means for gripping known in the art can be used as well.
In yet another aspect, the invention includes a method for adjusting the distance between two vertebrae using the vertebral distractor described above. The method comprises the steps of engaging the vertebral distractor having at least one tracking array which has tracking elements with the vertebrae and then increasing the distance between the vertebrae by moving the second arm away from the first arm. A surgical navigation system with a computer controller and a position sensing unit is employed to communicate with the tracking elements of the tracking array on the vertebral distractor thereby creating a reference point for the vertebral distractor. Further, the location of each individual vertebrae element can be registered by contacting the vertebrae with a trackable instrument such as a registration probe. In a preferred embodiment the optically tracked instrument is a digitizer probe.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in this description.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.